Leisure-time physical activity and risk of sudden cardiac death: a 28-year follow-up from the Copenhagen City Heart Study.

Background: Sudden cardiac death (SCD) remains a major public health challenge, yet the long-term association of leisure-time physical activity with SCD risk is not well established. We examined whether self-reported leisure-time physical activity is associated with SCD incidence over 28 years, accounting for competing risks from non-SCD mortality and time-updated changes in leisure-time physical activity. Methods: We included 10,100 participants from the Copenhagen City Heart Study, examined in 1991-1994 and followed until 31 December 2021. SCD events were identified from Danish death certificates using a standardized protocol. Leisure-time physical activity was self-reported at baseline and at 10-year follow-up and incorporated as a time-updated exposure, categorized as low, moderate, or high. Cause-specific Cox models estimated associations with SCD, adjusting for age, sex, smoking, alcohol, and socioeconomic factors. Cumulative incidence was standardized to the Danish population, and population attributable risk for low activity was calculated. This study is registered at ClinicalTrials.gov (NCT02993172). Findings: During a median follow-up of 28.6 years, 897 SCD events occurred among 10,100 participants (mean age 60.8 years; 56% women). Twenty-year standardized cumulative incidence rose with lower activity. In time-updated analyses, moderate and high leisure-time physical activity were associated with lower SCD risk compared with low activity (hazard ratio (HR) of 0.60, 95% confidence interval (CI) 0.50-0.72; and HR 0.50, 95% CI 0.41-0.62, respectively). After 25 years, 33% (95% CI 21-46%) of SCD could be attributed to low activity. Interpretation: Higher leisure-time physical activity is associated with lower long-term risk of SCD in this observational cohort. These findings support the potential public health relevance of promoting leisure-time physical activity, although causality cannot be established. Funding: Research Fund of Tokai University Educational System, Asahikawa Medical University Alumni Fund, Danish Heart Foundation, Birthe and John Meyer Family Foundation, Novo Nordisk Foundation.